A general problem of effectively and efficiently cleaning the bottom surface of a pool exists where dirt and debris is heavy and/or when the pool has not been regularly cleaned. The movement of water through the inlet ports formed in the bottom or baseplate of the pool cleaner may not be sufficient to create the required turbulence at the surface to disturb and lift the dirt and debris into suspension so that it can be drawn into the water inlet port.
To address this problem, self-propelled swimming pool cleaners have been equipped with nozzles which discharge pressurized streams of water (i.e., water jets) that are directed at, and stir up debris on the surface of a pool beneath the pool cleaner. For example, commonly assigned U.S. Pat. No. 7,316,751 addresses this problem and discloses a method of lifting dirt and debris off the surface beneath the pool cleaner by discharging a pressurized stream of water at the pool surface beneath the cleaner via one or more directional cleaning water jet nozzles. Debris resting on the pool surface that is contacted by the pressurized stream is lifted into suspension beneath the cleaner and the water and suspended debris is drawn through the water inlet port in the base and is subsequently captured by the cleaner's filter or an external filter that is remote from the cleaner.
Commonly assigned U.S. Pat. No. 8,434,182 discloses a cleaning apparatus that utilizes a reversible jet drive valve to direct a propulsion water jet stream from a pump through a discharge conduit to thereby propel the cleaner along the surface of the pool. The jet drive valve additionally includes a pair of opposing ports in fluid communication with one or more lengths of tubing to deliver pressurized water to one or more nozzles mounted at opposing ends of the housing. The one or more nozzles discharge water jets towards the surface to stir up dirt and debris on the surface of the pool beneath the cleaner. Alternatively, a propeller pump and a centrifugal pump functioning as an impeller are both mounted coaxially along a single drive shaft of an electric motor. The centrifugal pump provides the pressurized water jet stream, via tubing, to nozzles mounted at the front end of the housing for stirring up dirt and debris on the surface of the pool beneath the cleaner.
In addition, commonly assigned published application US 20130092193 similarly discloses the propeller pump and a centrifugal pump functioning as an impeller which are both mounted coaxially along a single drive shaft of an electric motor to provide pressurized water, via tubing, to a cleaning apparatus base having at least one water inlet port and a transversely positioned conduit having a plurality of outlet openings. The outlet openings are spaced apart and discharge pressurized streams of water beneath the base in a direction generally normal to the longitudinal axis of the cleaner. The pressurized streams stir up dirt and debris on the surface of the pool beneath the cleaner and the debris is drawn into the cleaner through the water inlet port.
The utilization of pressurized streams of water directed under the base of the cleaner have been effective to raise and draw the dirt and debris into the cleaner for filtering has been very effective. However, the coaxial mounting of the centrifugal pump directly on the drive shaft of the electric motor produces a high rotational rate which can lead to reducing the useful life of the centrifugal pump and the inconvenience and expense of its replacement.